Technical Abstract:
In recent years considerable numbers of foodborne disease outbreaks associated with produce were reported and specifically Tomatoes have been involved with a number of multi state outbreaks. The purpose of this study was to evaluate efficacy of integrated treatment of UVC and low dose Gamma radiation to inactivate inoculated mix Strains of Escherichia coli O157:H7 and Salmonella enterica on whole Grape tomatoes.
A mix bacterial cocktail composed of a three strain mixture of E. coli O157:H7 (C9490,
E02128 and F00475) and a three serotype mixture of S. enterica (S. Montevideo G4639, S. Newport H1275, and S. Stanley H0558) were used for this study. Spot inoculation (50-100 microliter) of tomatoes (surface and stem sites) was performed to achieve population of appropriately 107 CFU/tomato. Inoculated tomatoes were subjected to UVC (253.7 nm) dose of 0.6 KJ/M2 followed by four different low doses of gamma radiations ( 0.1 kGy, 0.25 kGy, 0.5 kGy, 0.75 kGy). The quality aspect (lycopene content, color, and texture) and the fate of background microflora (mesophilic, psychrotrophic, mold and yeast counts) during
storage at room temperature ( 22C, 60% RH) over 21 days were also determined.
Integrated treatment with UVC light plus low dose radiation significantly (p < 0.05) reduced the population of the target pathogens on whole Grape tomato. Results indicate about 3.40.27 and 3.00.12 log CFU reduction of E. coli O157:H7, and S. enterica per tomato was achieved with UVC treatment (0.6 KJ/M2) combined with 0.25 kGy radiation. Even better, more than a 5 or 6 log CFUreduction per fruit was accomplished by combining UVC treatment with 0.5 kGy and 0.75 kGy radiation respectively for all tested pathogens. Furthermore, UVC light treatment with Gamma radiation significantly (p less than 0.05) reduced the native microflora on tomatoes.
Data obtained from this work presents efficacious treatment strategy for produce.